An apparatus and method are disclosed for error correction code (“ECC”) striping. A memory receives sets of data in an original order. The memory stores the sets of data row by row in rows and columns such that user data in each row follows the original order. Each set of data is stored in a different row. An ecc data generator is coupled to the memory. The ecc data generator generates ecc data for each set of data in each row. The ecc data generator appends the generated ecc data to an end of each corresponding row. A modulator device is also coupled to the memory. The modulator device extracts the combined sets of data and ecc data in a striped order comprising a column by column order. A column comprises data from each row.
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1. A method comprising:
receiving user data in an original order;
organizing the user data row by row into rows and columns such that user data in each row follows the original order;
calculating error correction code (“ECC”) data for the user data in each row;
appending the ecc data to an end of each row, wherein the ecc data calculated for a corresponding row is appended to an end of the corresponding row; and
sending the user data and the appended ecc data to a data storage device in a striped order, the striped order comprising a column by column order, a column comprising data from each row.
3. An encoder comprising:
a memory that receives sets of data in an original order and stores the sets of data row by row in rows and columns wherein each set of data is stored in a row in the original order;
an error correction code (“ECC”) data generator coupled to the memory, the ecc data generator generating ecc data for each set of data, the ecc data generator appending the generated ecc data for a set of data to an end of a row corresponding to the set of data; and
a device coupled to the memory, the device extracting the sets of data and the appended ecc data in a striped order, the striped order comprising a column by column order, a column comprising data from each row.
2. The method of
4. The encoder of
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The invention relates to the field of error correction codes, and in particular to applications traditionally requiring product error correction codes.
An error correction code (ECC) assists in locating errors in digital data, and allows a predetermined number of errors to be corrected. The ability to detect and correct errors is accomplished by adding redundant information to the data according to a specific algorithm. Each bit of redundant information is generated based on the original data bits.
Block error correction codes are used for fixed-size blocks of data. Examples of block error correction codes include Reed-Solomon, Golay, and Hamming codes. Block codes are widely used to protect the accuracy of data stored on digital storage media, or transmitted digitally.
In error correction coding, each block of data may be organized into rows and columns. In order to increase the number and range of possible errors that can be corrected by the ECC scheme in a block of data, error correction data is often calculated both for each row and for each column of data in the block. This method of using both row and column error correction codes in a single block of data is referred to as a product code or a two dimensional block error correction code. The increase in ability to correct errors using a product code also introduces an increase in the amount of redundant information added to the data since ECC data must be added for both rows and columns. This increase in the amount of error correction data in turn decreases the amount of original user data that can be stored or transmitted.
As illustrated in
Some errors can be corrected using only the row ECC data, but if an individual row contains too many errors for the respective row ECC scheme to correct, then the column ECC data must also be used to correct the errors. This means that in most cases the entire block is accessed whenever any of the user data is accessed.
Many applications frequently involve errors that require both the row and column ECC data to correct. Errors due to scratches or other defects in digital storage media, or due to certain types of interference in either wired or wireless digital communications are more likely to occur in groups than individually. Although using a product code as described can correct a large amount of contiguous errors, a significant overhead of additional ECC data is introduced by the scheme. This data overhead decreases the actual user data storage capacity or throughput and increases the overall complexity of the system.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that correct errors in groups of contiguous data. Beneficially, such an apparatus, system, and method would also decrease the amount of ECC data used to detect and correct errors.
The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available ECC systems. Accordingly, the present invention has been developed to provide an apparatus and method that overcome many or all of the above-discussed shortcomings in the art.
A method of the present invention is presented for ECC striping. In one embodiment, the method includes receiving user data in a first ordered manner. The method also may include organizing said user data into rows and columns. In a further embodiment, the method includes calculating ECC data for each of said rows. The method, in another embodiment, includes appending said ECC data to each of said rows wherein the ECC data calculated for a given of said rows is appended to that specific given of said rows. In one embodiment, the method includes sending combined user data and ECC data in a second ordered manner.
In one embodiment, receiving user data comprises receiving user data having an initial set of ECC data included therein. In a further embodiment, the step of sending combined user data and ECC data comprises sending combined user data and ECC data column by column.
An encoder apparatus is provided with a plurality of modules configured to functionally execute the necessary steps of encoding ECC striping. These modules in the described embodiments include a memory, an ECC data generator, and a device.
The memory, in one embodiment, is configured to receive sets of data in a first ordered manner. In a further embodiment, the memory stores the sets of data in rows and columns. The memory, in another embodiment, stores each set of data in a different row from the other sets of data. In one embodiment, the data has an initial set of ECC data included therein, in a further embodiment, the memory is also part of a decoder.
The ECC data generator, in one embodiment, is coupled to the memory. In another embodiment, the ECC data generator generates ECC data for each of the sets of data in each of the rows. In a further embodiment, the ECC data generator appends the generated ECC data to the set of data for its respective row.
The device, in one embodiment, is coupled to the memory. In a further embodiment, the device extracts the combined sets of data and ECC data in a second ordered manner. In one embodiment, the device extracts the combined sets of data and ECC data column by column. In another embodiment, the device comprises a modulator that modulates the combined sets of data and ECC data for a specific channel.
A decoder apparatus is provided with a plurality of modules configured to functionally execute the necessary steps of decoding ECC striping. These modules in the described embodiments include a first device, a memory, an ECC decoder and data corrector, and a second device.
The first device, in one embodiment, extracts data encoded in a first ordered manner. In a further embodiment, the first ordered manner is column by column. In another embodiment, the first device comprises a demodulator that demodulates the data from a specific channel. Each set of data, in one embodiment, has an initial set of ECC data included therein.
The memory, in one embodiment, is coupled to the first device. In another embodiment, the memory receives the encoded data. In one embodiment, the memory stores the data in rows and columns in a second ordered manner such that each of the rows contain a set of data and ECC data calculated for the set of data. In a further embodiment, the memory is also part of an encoder circuit. The second device, in one embodiment, extracts the sets of data in the second ordered manner.
The ECC decoder and data corrector, in one embodiment, are coupled to the memory. In another embodiment, the ECC decoder and data corrector receive the data from the memory in the second ordered manner. The ECC decoder and data corrector, in a further embodiment, use the ECC data to correct errors in the set of data, and send the error corrections to the memory.
These features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
The present invention decreases the amount of ECC data required to detect and correct errors in digital data while still maintaining a specified ability to correct errors in large groups of contiguous data. The present invention accomplishes this by placing distance either in space or in time between related symbols. Related symbols are symbols that are grouped together mathematically for ECC calculations. An error affecting contiguous symbols, like scratches or other defects in digital storage media, or certain types of interference in either wired or wireless digital communications, would affect many ECC groups, but would only affect one symbol from each group. Because only one symbol from each group is affected, the error can easily be corrected using a one dimensional ECC, removing the need for the two dimensional product code ECC and its data overhead.
As can be seen in
The block of data is then written to the digital storage media or transmitted. The first symbol to be written or transmitted is again the symbol occupying row 1 (120), column 1 (110). Instead of proceeding along row 1 (120), the next symbol written or transmitted is the symbol occupying row 2 (124), column 1 (110). Each symbol in column 1 (110) is then stored or transmitted, ending with the symbol occupying row U (122) column 1 (110). Once column 1 (110) has been stored or transmitted, column 2 (116) is then transmitted, beginning with the symbol occupying row 2 (124), column 1 (110), and proceeding to the symbol occupying row U (122) column 2 (116). Each column is stored or transmitted, proceeding in order toward column Y (114) until the entire block, including column Y (114) has been stored or transmitted. This includes row ECC data 140, which is stored or transmitted by column in the same manner as user data 130. Prior to storage or transmission, the data may first be copied to a memory buffer in this new ECC striped order to facilitate the storing or transmitting step.
Because of the ECC striping, meaning the out of order column by column manner in which the data is stored or transmitted, the entire data block must be read or received in order to use the data in its original order, or to correct the data with the row ECC which is stored or transmitted last. The effect is the same as if row and column ECC data were produced using the product code scheme—an entire block of data must be read or received rather than an individual row of data.
Notice that because of the ECC striping, even if an entire column is lost to contiguous errors, only one symbol from each ECC group is lost, and can easily be corrected. The correction ability of the ECC scheme employed should be chosen based upon the number and type of errors expected.
An embodiment of the process flow of an encoder stage of the present invention is illustrated in
It should be noted that in applications where data is not read and written simultaneously, buffer memory 450 and striping buffers 430 and 431 from the encoder in
Although the description of the present invention has utilized various embodiments, it will be recognized that the present invention is not limited to the specific embodiments described. Rather, the present invention encompasses all variants incorporating the essence of the ideas presented in the above description.
A third embodiment of the present invention is structured similar to the second embodiment of
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